Using quantum optical sensors for determining the Earth’s gravity field from space

authored by: J. Müller, Hu Wu
Abstract: Quantum optical technology provides an opportunity to develop new kinds of gravity sensors and to enable novel measurement concepts for gravimetry. Two candidates are considered in this study: the cold atom interferometry (CAI) gradiometer and optical clocks. Both sensors show a high sensitivity and long-term stability. They are assumed on board of a low-orbit satellite like gravity field and steady-state ocean circulation explorer (GOCE) and gravity recovery and climate experiment (GRACE) to determine the Earth’s gravity field. Their individual contributions were assessed through closed-loop simulations which rigorously mapped the sensors’ sensitivities to the gravity field coefficients. Clocks, which can directly obtain the gravity potential (differences) through frequency comparison, show a high sensitivity to the very long-wavelength gravity field. In the GRACE orbit, clocks with an uncertainty level of 1.0 × 10 ^{- 18} are capable to retrieve temporal gravity signals below degree 12, while 1.0 × 10 ^{- 17} clocks are useful for detecting the signals of degree 2 only. However, it poses challenges for clocks to achieve such uncertainties in a short time. In space, the CAI gradiometer is expected to have its ultimate sensitivity and a remarkable stability over a long time (measurements are precise down to very low frequencies). The three diagonal gravity gradients can properly be measured by CAI gradiometry with a same noise level of 5.0 mE/Hz. They can potentially lead to a 2–5 times better solution of the static gravity field than that of GOCE above degree and order 50, where the GOCE solution is mainly dominated by the gradient measurements. In the lower degree part, benefits from CAI gradiometry are still visible, but there, solutions from GRACE-like missions are superior.
Organisation(s): Institute of Geodesy
QuantumFrontiers
Type: Article
Journal: Journal of geodesy
Volume: 94
ISSN: 0949-7714
Publication date: 24.07.2020
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Geophysics, Geochemistry and Petrology, Computers in Earth Sciences
Electronic version(s): https://doi.org/10.1007/s00190-020-01401-8 (Access: Open)
https://doi.org/10.15488/10716 (Access: Open)

BibTeX

@article{d6814bc070264e449032f8b50f333ef5,
title = "Using quantum optical sensors for determining the Earth{\textquoteright}s gravity field from space",
abstract = "Quantum optical technology provides an opportunity to develop new kinds of gravity sensors and to enable novel measurement concepts for gravimetry. Two candidates are considered in this study: the cold atom interferometry (CAI) gradiometer and optical clocks. Both sensors show a high sensitivity and long-term stability. They are assumed on board of a low-orbit satellite like gravity field and steady-state ocean circulation explorer (GOCE) and gravity recovery and climate experiment (GRACE) to determine the Earth{\textquoteright}s gravity field. Their individual contributions were assessed through closed-loop simulations which rigorously mapped the sensors{\textquoteright} sensitivities to the gravity field coefficients. Clocks, which can directly obtain the gravity potential (differences) through frequency comparison, show a high sensitivity to the very long-wavelength gravity field. In the GRACE orbit, clocks with an uncertainty level of 1.0 × 10 - 18 are capable to retrieve temporal gravity signals below degree 12, while 1.0 × 10 - 17 clocks are useful for detecting the signals of degree 2 only. However, it poses challenges for clocks to achieve such uncertainties in a short time. In space, the CAI gradiometer is expected to have its ultimate sensitivity and a remarkable stability over a long time (measurements are precise down to very low frequencies). The three diagonal gravity gradients can properly be measured by CAI gradiometry with a same noise level of 5.0 mE/Hz. They can potentially lead to a 2–5 times better solution of the static gravity field than that of GOCE above degree and order 50, where the GOCE solution is mainly dominated by the gradient measurements. In the lower degree part, benefits from CAI gradiometry are still visible, but there, solutions from GRACE-like missions are superior.",
keywords = "Atomic gradiometry, Gravity field, Optical clocks, Quantum optical sensors, Relativistic geodesy",
author = "J. M{\"u}ller and Hu Wu",
note = "Funding Information: Open Access funding provided by Projekt DEAL. This research was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany{\textquoteright}s Excellence Strategy – EXC-2123/1 (Project-ID: 390837967) and the Collaborative Research Center SFB 1128 “Relativistic Geodesy and Gravimetry with Quantum Sensors (geo-Q).” This work was also partly supported by the European Space Agency (ESA) project “Study of a CAI gradiometer sensor and mission concepts.” We gratefully acknowledge the International Space Science Institute (ISSI) for providing support to participate at international workshops on the topic of “Spacetime metrology, clocks and relativistic geodesy.” ",
year = "2020",
month = jul,
day = "24",
doi = "10.1007/s00190-020-01401-8",
language = "English",
volume = "94",
journal = "Journal of geodesy",
issn = "0949-7714",
publisher = "Springer Verlag",
number = "8",
}